For nucleic acid analyzing devices, new techniques for sequencing DNA and RNA are being developed.
With methods in common use today that employ electrophoresis, a cDNA fragment sample synthesized in advance through reverse transcription reaction of a DNA fragment or RNA sample for sequencing is prepared, electrophoresis is performed after performing a dideoxy reaction by the well-known Sanger method, and a molecular weight separation/expansion pattern is measured and analyzed.
In contrast, as presented in Non-Patent Document 1, there has recently been proposed a method for sequencing DNA or the like by immobilizing it on a substrate. In this method, a sample DNA fragment to be analyzed is randomly captured on the surface of the substrate one molecule at a time and extended by one base at a time, and the result thereof is detected by fluorescence microscopy, thereby determining the base sequence. Specifically, there is first performed a step in which a DNA polymerase reaction is caused using four kinds of dNTP derivatives (MdNTP) which, by being incorporated into a template DNA as substrates of DNA polymerases, are capable of terminating DNA strand nucleic acid synthesis by the presence of a protective group, and which have detectable labels. A step of detecting the incorporated MdNTP by way of fluorescence, etc., and a step of returning the MdNTP to an extendible state are subsequently performed. With these three steps as one cycle, the sample DNA is sequenced by repeating this cycle. With this technique, since DNA fragments can be sequenced one molecule at a time, it is possible to analyze a large number of fragments simultaneously, and analysis throughput can thus be increased. Further, with this scheme, since it is possible to sequence single DNA molecules, there is a possibility that sample DNA purification and amplification in cloning, PCR, etc., which had been problematic in conventional techniques, may be rendered unnecessary, and faster genome analysis and genetic testing could be expected.